DESCRIPTION: (Adapted from the applicant's abstract.) The studies proposed will seek improvement of the immunogenicity of tumor cells by transfection with cDNAs for the recently identified co-stimulatory molecules B7 and the heat-stable antigen (HSA) and test if this approach may lead to the design of better anti-tumor vaccines. It would be determined whether transfection of tumor cells with these cell surface associated co-stimulatory molecules will improve the immunogenicity of tumor cells, whether the transfected tumor cells induce protective anti- tumor immune responses; whether they will induce autoimmunity; whether it is possible to identify tumor specific antigen using tumor cells with improved immunogenicity and if so, whether antigenic TSA peptides induce protective immune responses against the tumor.